// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef CONTENT_ZYGOTE_ZYGOTE_LINUX_H_
#define CONTENT_ZYGOTE_ZYGOTE_LINUX_H_

#include <stddef.h>

#include <string>
#include <vector>

#include "base/containers/small_map.h"
#include "base/files/scoped_file.h"
#include "base/memory/scoped_vector.h"
#include "base/posix/global_descriptors.h"
#include "base/process/kill.h"
#include "base/process/process.h"
#include "base/process/process_handle.h"
#include "base/time/time.h"

namespace base {
class PickleIterator;
}

namespace content {

class ZygoteForkDelegate;

// This is the object which implements the zygote. The ZygoteMain function,
// which is called from ChromeMain, simply constructs one of these objects and
// runs it.
class Zygote {
public:
    Zygote(int sandbox_flags, ScopedVector<ZygoteForkDelegate> helpers,
        const std::vector<base::ProcessHandle>& extra_children,
        const std::vector<int>& extra_fds);
    ~Zygote();

    bool ProcessRequests();

private:
    struct ZygoteProcessInfo {
        // Pid from inside the Zygote's PID namespace.
        base::ProcessHandle internal_pid;
        // Keeps track of which fork delegate helper the process was started from.
        ZygoteForkDelegate* started_from_helper;
        // Records when the browser requested the zygote to reap this process.
        base::TimeTicks time_of_reap_request;
        // Notes whether the zygote has sent SIGKILL to this process.
        bool sent_sigkill;
    };
    typedef base::SmallMap<std::map<base::ProcessHandle, ZygoteProcessInfo>>
        ZygoteProcessMap;

    // Retrieve a ZygoteProcessInfo from the process_info_map_.
    // Returns true and write to process_info if |pid| can be found, return
    // false otherwise.
    bool GetProcessInfo(base::ProcessHandle pid,
        ZygoteProcessInfo* process_info);

    // Returns true if the SUID sandbox is active.
    bool UsingSUIDSandbox() const;
    // Returns true if the NS sandbox is active.
    bool UsingNSSandbox() const;

    // ---------------------------------------------------------------------------
    // Requests from the browser...

    // Read and process a request from the browser. Returns true if we are in a
    // new process and thus need to unwind back into ChromeMain.
    bool HandleRequestFromBrowser(int fd);

    void HandleReapRequest(int fd, base::PickleIterator iter);

    // Get the termination status of |real_pid|. |real_pid| is the PID as it
    // appears outside of the sandbox.
    // Return true if it managed to get the termination status and return the
    // status in |status| and the exit code in |exit_code|.
    bool GetTerminationStatus(base::ProcessHandle real_pid, bool known_dead,
        base::TerminationStatus* status,
        int* exit_code);

    void HandleGetTerminationStatus(int fd,
        base::PickleIterator iter);

    // This is equivalent to fork(), except that, when using the SUID sandbox, it
    // returns the real PID of the child process as it appears outside the
    // sandbox, rather than returning the PID inside the sandbox.  The child's
    // real PID is determined by having it call content::SendZygoteChildPing(int)
    // using the |pid_oracle| descriptor.
    // Finally, when using a ZygoteForkDelegate helper, |uma_name|, |uma_sample|,
    // and |uma_boundary_value| may be set if the helper wants to make a UMA
    // report via UMA_HISTOGRAM_ENUMERATION.
    int ForkWithRealPid(const std::string& process_type,
        const base::GlobalDescriptors::Mapping& fd_mapping,
        const std::string& channel_id,
        base::ScopedFD pid_oracle,
        std::string* uma_name,
        int* uma_sample,
        int* uma_boundary_value);

    // Unpacks process type and arguments from |iter| and forks a new process.
    // Returns -1 on error, otherwise returns twice, returning 0 to the child
    // process and the child process ID to the parent process, like fork().
    base::ProcessId ReadArgsAndFork(base::PickleIterator iter,
        std::vector<base::ScopedFD> fds,
        std::string* uma_name,
        int* uma_sample,
        int* uma_boundary_value);

    // Handle a 'fork' request from the browser: this means that the browser
    // wishes to start a new renderer. Returns true if we are in a new process,
    // otherwise writes the child_pid back to the browser via |fd|. Writes a
    // child_pid of -1 on error.
    bool HandleForkRequest(int fd,
        base::PickleIterator iter,
        std::vector<base::ScopedFD> fds);

    bool HandleGetSandboxStatus(int fd,
        base::PickleIterator iter);

    // Attempt to reap the child process by calling waitpid, and return
    // whether successful.  If the process has not terminated within
    // 2 seconds of its reap request, send it SIGKILL.
    bool ReapChild(const base::TimeTicks& now, ZygoteProcessInfo* child);

    // Attempt to reap all outstanding children in |to_reap_|.
    void ReapChildren();

    // The Zygote needs to keep some information about each process. Most
    // notably what the PID of the process is inside the PID namespace of
    // the Zygote and whether or not a process was started by the
    // ZygoteForkDelegate helper.
    ZygoteProcessMap process_info_map_;

    const int sandbox_flags_;
    ScopedVector<ZygoteForkDelegate> helpers_;

    // Count of how many fork delegates for which we've invoked InitialUMA().
    size_t initial_uma_index_;

    // This vector contains the PIDs of any child processes which have been
    // created prior to the construction of the Zygote object, and must be reaped
    // before the Zygote exits. The Zygote will perform a blocking wait on these
    // children, so they must be guaranteed to be exiting by the time the Zygote
    // exits.
    std::vector<base::ProcessHandle> extra_children_;

    // This vector contains the FDs that must be closed before reaping the extra
    // children.
    std::vector<int> extra_fds_;

    // The vector contains the child processes that need to be reaped.
    std::vector<ZygoteProcessInfo> to_reap_;
};

} // namespace content

#endif // CONTENT_ZYGOTE_ZYGOTE_LINUX_H_
